Messages in this thread |  | | Date | Wed, 28 Aug 2002 17:04:33 +0200 | From | Frank.Otto@tc ... | Subject | Re: PROBLEM: conflict between apm and system clock on Inspiron 8100 |
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Alan Cox wrote: > On Mon, 2002-08-26 at 18:00, mike heffner wrote: > > Well, isn't that a nice feature. Is there a > > workaround for this hardware? > > A thinkpad ;)
Unfortunately, that's not true -- I just got an IBM Thinkpad R32 which exhibits the same behaviour as Mike's Dell Inspiron 8100, it's only a tad worse. When I have the battstat_applet running (which checks the battery every second), kernel time runs about 3% slow compared to the RTC (which seems to be half-way accurate on my machine).
The cause seems to be definitely APM. If I shut off battstat_applet and apmd, kernel time and RTC are in sync. With only apmd, I lose about 15 seconds per hour. With battstat_applet, I lose 2 minutes per hour. With while true; do cat /proc/apm >/dev/null; done the system runs at about 1/4 of the right speed. Using a kernel with ACPI eliminates the problem (of course, you lose almost all power management functionality too).
BTW, I have set CONFIG_APM_ALLOW_INT, and on startup the kernel even says "IBM machine detected. Enabling interrupts during APM calls." Doesn't seem to help, though.
Alan Cox continues: > In theory you could try writing some code to measure the elapsed time by > other means and then correct the kernel for the number of lost ticks. > Not trivial. Or for that matter dont run battstat
I've hacked together a small daemon that tries to adjust the value and speed of the kernel clock (via adjtimex) to the RTC. An ugly solution, I know, but better than nothing. If anyone is interested, mail me.
Regards, Frank
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